+2008-03-06 Paolo Bonzini <bonzini@gnu.org>
+
+ * simplify-rtx.c (simplify_subreg): Remove useless shifts from
+ word-extractions out of a multi-word object.
+
2008-03-06 Richard Guenther <rguenther@suse.de>
* tree.def (BIT_FIELD_REF): Constrain result type and its precision.
return simplify_gen_binary (ASHIFT, outermode,
XEXP (XEXP (op, 0), 0), XEXP (op, 1));
+ /* Recognize a word extraction from a multi-word subreg. */
+ if ((GET_CODE (op) == LSHIFTRT
+ || GET_CODE (op) == ASHIFTRT)
+ && SCALAR_INT_MODE_P (outermode)
+ && GET_MODE_BITSIZE (outermode) >= BITS_PER_WORD
+ && GET_MODE_BITSIZE (innermode) >= (2 * GET_MODE_BITSIZE (outermode))
+ && GET_CODE (XEXP (op, 1)) == CONST_INT
+ && (INTVAL (XEXP (op, 1)) & (GET_MODE_BITSIZE (outermode) - 1)) == 0
+ && byte == subreg_lowpart_offset (outermode, innermode))
+ {
+ int shifted_bytes = INTVAL (XEXP (op, 1)) / BITS_PER_UNIT;
+ return simplify_gen_subreg (outermode, XEXP (op, 0), innermode,
+ (WORDS_BIG_ENDIAN
+ ? byte - shifted_bytes : byte + shifted_bytes));
+ }
+
return NULL_RTX;
}